1. Field of the Invention
The present invention relates to an improved flat type vibrator motor used as a silent call means of a mobile communications apparatus and an improved eccentric rotor which is one of the major members thereof.
2. Description of the Related Art
A conventional cylindrical DC motor, which is used as a silent call means of a pager or mobile phone, is shown in FIG. 8. As shown in the drawing, an eccentric weight W formed of tungsten alloy is installed at an output shaft S of a cylindrical DC motor M. When the motor M rotates, vibrations are generated by the centrifugal force of the eccentric weight W.
However, this conventional method of adding the eccentric weight W to the output shaft S has disadvantages. That is, when an apparatus such as a pager is designed, a space for rotation of the eccentric weight W should be considered. Also, since an expensive tungsten alloy is used, the manufacturing cost increases.
Recently, there is a need for a small cylindrical DC motor and a motor having a diameter of 4 mm is being used. However, although a main body of a motor has a diameter of 4 mm, the diameter of a space for rotation of the eccentric weight provided at the output shaft should be at least 6 mm to obtain a sufficient amount of vibration. Also, since the cylindrical motor cannot be mounted in a mobile phone as it is, an additional installation member is usually needed. Thus, the cylindrical motor requires a large space, which makes it difficult to manufacture a mobile apparatus which is thin.
Furthermore, while a great deal of current is consumed, its efficiency is a mere 20-30%. Accordingly, a flat type motor which can secure a thickness less than 3 mm is being widely noted.
The subject applicant has suggested a flat type coreless vibrator motor in Japanese Patent No. 2,137,724 and U.S. Pat. No. 5,036,239. In the flat type coreless vibrator motor, an output shaft protruding outside the motor is removed and one of three air-core coils symmetrically arranged on a rotary commutator member is installed at the opposite side of the commutator member, so that the three air-core coils are grouped together and eccentricity is achieved by inclining the rotor itself.
Since an effective conductive body of an armature coil of the above motor is long, a relatively high efficiency can be obtained. The motor is designed such that a current of about 10 mA flows at a voltage of 3 V. Also, since the output shaft and the eccentric weight do not protrude outside the motor, there is no great limit in space. However, since three wound type air-core coils are provided at one surface of the commutator member, the size of the air-core coils needs to be reduced. Thus, the number of parts and steps increases.
In the above flat type motor having a built-in type eccentric rotor where three armature coils are grouped together, as the motor becomes smaller, the interval between the armature coils decreases so that connecting the end portions of the armature coils to the commutator with no damage to the armature coils is very difficult. Also, since each of the armature coils needs to fit within an angle between the adjacent magnetic poles of a magnet, improvement of efficiency is further required. Also, since there are three wound type air-core coils, the number of parts increases.
Recently, as mobile phones become smaller, a great amount of vibration as a silent call means is not needed any more.
To solve the above-described problems, it is a first object of the present invention to provide a disc eccentric rotor which appropriately generates vibrations by centrifugal force with high efficiency and can be easily installed, and a flat vibrator motor using the same.
It is a second object of the present invention to provide a disc eccentric rotor which does not need an eccentric member by arranging the center of gravity of the rotor to be eccentric by using the coils themselves.
It is a third object of the present invention to provide a flat vibrator motor which uses the above flat, disc eccentric rotor so that high efficiency is achieved, the number of parts is reduced, and manufacturing cost is lowered.
It is a fourth object of the present invention to produce vibrations by using a difference in centrifugal forces, which is achieved by arranging a metal member having a high specific gravity at a portion where no wound air-core coils exist.
To achieve the foregoing objects, a first disc eccentric rotor having two or more air-core coils and generating a difference in centrifugal forces by the rotation of the rotor itself, is provided, the rotor comprising a flat commutator member having a shaft insertion through hole in the center thereof, a plurality of commutator land segments formed around the shaft insertion through hole on a first side of the flat commutator member, wound air-core coil arrangement guides outside the shaft insertion through hole on a second side of the flat commutator member, air-core coil end portion connection lands circumferentially on the second side of the flat commutator member, a shaft holder installed around the shaft insertion through hole on the second side of the flat commutator member, and wound air-core coils installed at the wound air-core coil arrangement guides and having the end portions connected to the air-core coil end portion connection lands.
In the rotor, the air-core coils are radially arranged at a predetermined angle and at least one air-core coil is a printed wiring air-core coil.
Further, the air-core coils comprise one printed wiring air-core coil and two wound air-core coils, and the air-core coils are arranged so as not to overlap one another. Otherwise, the air-core coils comprise two printed wiring air-core coils and one wound air-core coil, and the air-core coils are arranged so as not to overlap one another.
It is preferable that the wound air-core coil arrangement guide apertures and reinforcement holes are on the printed wiring commutator member, and the reinforcement holes and the wound air-core coil arrangement guide apertures are respectively connected through grooves.
Moreover, it is preferable that the shaft holder and the wound air-core coil arrangement guides are integrally formed of the same resin by outsert molding on the flat commutator member.
As another way to achieve the foregoing objects, a second disc eccentric rotor having one or more wound air-core coils and generating a difference in centrifugal forces by the rotation of the rotor itself, is provided, the rotor comprising a flat commutator member having a shaft insertion through hole in the center thereof, a plurality of commutator land segments formed around the shaft insertion through hole on a first side of the flat commutator member, a shaft holder installed around the shaft insertion through hole on a second side of the flat commutator member, wound air-core coil end portion connection lands formed circumferentially on the second side of the flat commutator member, at least one wound air-core coil installed outside the shaft holder on the second side of the flat commutator member and having the end portions thereof connected to the wound air-core coil end portion connection lands, and an eccentric weight formed of tungsten alloy installed within the thickness of the wound air-core coil on the second side of the flat commutator member, the weight being fixed to the flat commutator member by resin.
Further, in the second disk eccentric rotor, at least one printed wiring coil is at a position of the flat commutator member where the eccentric weight is installed.
As yet another way to achieve the foregoing objects, there is provided a flat vibrator motor having the eccentric rotor as described above. Here, the flat vibrator motor comprises a disc eccentric rotor having at least one air-core coil and generating a difference in centrifugal forces by the rotation of the rotor itself, a shaft for supporting the eccentric rotor, a magnet for providing a magnetic field for the rotor via a gap therebetween in an axial direction, a brush arranged inside the magnet for providing electric power to the air-core coil through the flat commutator member, and a housing accommodating all the elements described above.
In the flat vibrator motor, the shaft is fixed at one side of the housing and a member for preventing the eccentric rotor from moving in a radial direction is installed at the other side of the housing.
Since the rotor is of a disc, the size of each air-core coil can be set such that the effective conductive portions can be positioned within an open angle of two adjacent magnetic poles. Therefore, the maximum vibrations are generated so as to secure high efficiency. The open angle of two adjacent magnetic poles are called xe2x80x9cstandard electric open angle.xe2x80x9d The connection of the coil end portions can be easily performed. Also, the disc rotor can be eccentric.
The rotor is not arranged to be inclined toward the side. The size of each air-core coil can be set such that the effective conductive portions can be positioned within the standard electric open angle. Also, since the eccentricity due to the difference in weight between the printed wiring air-core coil and the wound air-core coil can be anticipated, a disc rotor which can easily generate vibrations due to the difference in the centrifugal forces during rotation is possible.
Since the eccentricity due to the difference in weight between the printed wiring air-core coil and the wound air-core coil can be anticipated, a disc rotor which can easily generate vibrations due to a difference in the centrifugal forces during rotation is possible. Also, since one or two wound air-core coils suffice, the manufacturing cost can be reduced.
When the shaft holder and the wound air-core coil arrangement guides are erected by outsert molding on the wound air-core coil arrangement guide apertures and the reinforcement holes, resin fills the insertion pass portion so that the wound air-core coil arrangement guides, the stop walls, and the shaft holder are integrally connected, which improves strength.
The shaft holder and the wound air-core coil arrangement guides can be formed simultaneously.
A disc rotor according to the invention can generate large vibrations due to high specific gravity of tungsten alloy. Since fewer air-core coils are required, the manufacturing cost is reduced.
Since the vibrator motor has the above-described rotor, the manufacturing cost is reduced while large vibrations can be obtained.